This invention relates generally to a fluid discharge valve assembly located at the fluid discharge nozzle end of a pump sprayer which may he trigger actuated, and more particularly to a two-stage pressure build-up discharge valve assembly for regulating the operator's pumping stroke velocity to thereby effect a well defined spray particle size and distribution range of fluid spray out of the discharge orifice.
Many known pump sprayers have discharge valves at the nozzle end of the discharge passage for throttle valving the fluid pressure during pumping. Such discharge valve forms part of an assembly including a spinner probe having spin mechanics of some type to effect a spinning or swirling action of the pressurized fluid to produce a spray discharge out of the orifice. Resilient means in the form of a separate coil spring or an integral plastic molded spring is provided for urging the valve into its seated position. The valve opens in response to fluid pressure in the discharge passage which exceeds the closing force of the spring.
Such known sprayer discharge valves are typically of the throttling type which permit the operator to control the actuation rate of the trigger sprayer, which actuation rate determines the flow velocity. The flow velocity through the spin mechanics determines the size of the spray plume or more precisely the rotational velocity of the annular fluid sheet exiting from the orifice. The greater the velocity (the more energy in the spray plume) the thinner the annular sheet and the finer the particles created by breakup in the atmosphere. Thus the operator's pumping stroke rate varies the size and distribution range of the spray particles.
New product formulations require a narrow distribution range of particles and a predicted mean particle size.